The present invention relates to a device for transmitting optical data, which is installed in both of an automated guided vehicle and a manufacturing machine so as to transmit data necessary for delivery of a transfer object by two-way communication within a transportation system having an interlocking mechanism, and more particularly relates to a device for transmitting optical data, which includes a non-volatile memory for recording and holding a communication log, reads the communication log when a trouble occurs and promptly investigates the cause of the trouble.
On the manufacturing line of a semiconductor device or a liquid crystal display, semiconductor wafers or the substrates of the liquid crystal display are transferred to a plurality of manufacturing machines arranged in a building by an automated guided vehicle according to the process.
FIGS. 6(a), 6(b) and 6(c) show the states of delivery of a carrier 4 as a transfer object storing a semiconductor wafer 3 between an automated guided vehicle 1 and a semiconductor manufacturing machine 2 by an AMHS (Automated Material Handling System) on a manufacturing line of a semiconductor device. FIG. 6(a) shows a state in which the automated guided vehicle 1 is a self-running AGV (Automated Guided Vehicle) that runs on wheels and the carrier 4 is loaded on the semiconductor manufacturing machine 2 by an arm 5 and a hand 6 of the AMHS. FIG. 6(b) shows a state in which the automated guided vehicle 1 is an RGV (Rail Guided Vehicle) that runs along a guide rail 7 fixed to the floor and the carrier 4 is loaded in the same manner as above by the AMHS. FIG. 6(c) shows a state in which the automated guided, vehicle 1 is an OHT (Overhead Hoist Transport) that runs along a guide rail 8 fixed to the ceiling and the carrier 4 is loaded by a hoist 9 and a hand 10 of the AMHS.
The above-mentioned delivery of the carrier 4 is performed by host computers installed in the automated guided vehicle 1 and the semiconductor manufacturing machine 2, respectively, according to the instructions from a control system that controls the entire manufacturing line. During the delivery, it is necessary to operate the automated guided vehicle 1 and the semiconductor manufacturing machine 2 interactively. Therefore, sending and receiving of necessary data are performed by optical data transmission devices 11 installed in both of the automated guided vehicle 1 and the semiconductor manufacturing machine 2.
The optical two-way communication between the automated guided vehicle 1 and the semiconductor manufacturing machine 2 s carried out when the automated guided vehicle 1 reaches a position where it faces the semiconductor manufacturing machine 2. The contents of this communication when loading the carrier 4 from the automated guided vehicle 1 on the semiconductor manufacturing machine 2 are such that the automated guided vehicle 1 sends transfer port specifying signals (CS_0, CS_1), a port use signal (VALID), a transfer request signal (TR_REQ), a busy signal (BUSY) and a complete signal (COMPT) to the semiconductor manufacturing machine 2, and the semiconductor manufacturing machine 2 sends an acceptance request signal (L_REQ) and an acceptance permission signal (READY) to the automated guided vehicle 1. These signals continue to be sent or received during a period of time when the delivery of he carrier 4 is being carried out.
Similarly, on the manufacturing line of a liquid crystal display, since the liquid crystal display is manufactured by similar processing steps though a glass substrate of a slightly larger size is used instead of the semiconductor wafer 3, the transfer is performed in the manner similar to that shown in FIGS. 6(a), 6(b) and 6(c).
Since the transfer objects of these manufacturing lines are very expensive and easily broken, it is necessary to handle them carefully so as not to give them shock. Hence, the transportation system for them has an interlocking mechanism that immediately suspends the transfer operation when some trouble occurs.
In the above-mentioned transportation system, when a trouble occurs due to some cause, the interlocking function is performed to suspend the operation for safe reasons. Although the frequency of occurrence of trouble is low, it is unknown when and where trouble occurs. In this case, it is necessary to investigate the cause of trouble and deal with the cause so as to prevent reoccurrence of the same trouble.
This interlocking performed due to a trouble often occurs during the delivery of the transfer object which is carried out by executing a plurality of steps by each of the automated guided vehicle and the manufacturing machine while performing data transmission therebetween. The host computer activates the interlocking function of its own vehicle or device immediately when a trouble occurs in its own vehicle or device. On the other hand, when a trouble occurs in the vehicle or device of the other host computer, the host computer detects the trouble from a fact that a response to the sent signals has not been received in a certain period of time, and activates the interlocking function.
Thus, when the interlocking function is activated, if it is possible to identify which step of the delivery of the transfer object involves with the trouble from the contents of data sent or received just before the occurrence of trouble, the cause can be investigated relatively easily.
However, a conventional optical data transmission device does not have a function of recording the communication history. Hence, if the transportation system is suspended, it is necessary to investigate the whole system and thus it takes a long time for recovery, causing a considerable lowering of the manufacturing efficiency of the manufacturing line.
An object of the present invention is to provide a device for transmitting optical data, which records a communication log for a certain period of time and reads the communication log when a trouble occurs so as to promptly investigate the cause of the trouble.
The present invention is a device for transmitting optical data, which is installed in both of an automated guided vehicle and a plurality of manufacturing machines arranged on a manufacturing line so as to transmit data necessary for delivery of a transfer object by two-way communication within a transportation system having an interlocking mechanism for suspending an operation when a trouble occurs and transporting the transfer object to the manufacturing machines by the automated guided vehicle, characterized by including: a non-volatile memory for recording and holding a communication log; and communication log recording means for writing a communication log in the non-volatile memory and outputting the recorded contents of the communication log to an external device when there is an inquiry from the external device.
The communication log stored in the non-volatile memory is a historical record of two-way data communication performed between the automated guided vehicle and the manufacturing machine during one delivery, and records the steps until the transportation system suspends the operation by interlocking. Therefore, if the communication log is read when a trouble occurred, it is possible to know the process of the delivery operation performed between the automated guided vehicle and the manufacturing machine until the interlocking occurred. Consequently, the cause of the trouble can be promptly investigated.
Incidentally, at least one of the devices for transmitting optical data installed in the automated guided vehicle and manufacturing machine need to have the communication log recording means.
In the above-described structure, it is possible to allow the non-volatile memory to have a storage capacity capable of recording a series of communication log for one delivery and the communication log recording means to clear the recorded contents of the non-volatile memory when starting the communication for the delivery of the transfer object and then start recording a series of communication log.
This arrangement is made because the communication log of one delivery performed just before the occurrence of a trouble is necessary and sufficient for investigating the cause of the trouble. Accordingly, since only this communication log is to be stored, the storage capacity of the non-volatile memory is made smaller, thereby facilitating the investigation of the cause of the trouble.
Moreover, in the above-described structure, it is possible to allow the communication log recording means to include optical communication means for receiving an inquiry about a communication log from an external device through a light emitting and receiving device and for outputting the communication log recorded in the non-volatile memory in response to the inquiry.
This arrangement makes it possible to investigate the cause of a trouble immediately on the spot where the automated guided vehicle is suspended, by reading the communication log with the use of a portable light transmitter-receiver.
In the present invention the communication log of the optical data transmission performed during the delivery of the transfer object between the automated guided vehicle and the manufacturing machine is recorded in the non-volatile memory and the stored contents is allowed to be read, if necessary. Therefore, when a trouble occurs, it is possible to promptly investigate the cause of the trouble and recover the transportation system having the interlocking mechanism, thereby improving the manufacturing efficiency.
The nature, principle, and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals.